The FBI employs drones in domestic surveillance operations, Director Robert Mueller revealed, but said they were used in a “very, very minimal way.”

Mr Mueller, in Senate testimony on Wednesday, acknowledged for the first time that the Federal Bureau of Investigation uses “very few” drones in a limited capacity for surveillance.

“It’s very seldom used and generally used in a particular incident when you need the capability,” Mr Mueller said. “It is very narrowly focused on particularised cases and particularised needs.”

Mr Mueller’s remarks about the FBI’s use of drones — and the regular use of the vehicles by other law enforcement agencies — come as lawmakers and civil liberties groups are raising concerns about the reach of...